I. Field of the Invention
The present invention relates to wireless communication devices, and their production, testing, and use. More particularly, the present invention relates to a novel and improved dual purpose interface for a wireless communication device such as a cellular telephone which interfaces with an antenna in normal use, and interfaces with test equipment during production line testing.
II. Description of the Related Art
Wireless communication devices are becoming increasingly prevalent, with cellular telephones being a particularly notable example. With these devices, radio-frequency (RF) signals are produced and transmitted as well as received to create communication links between remote devices. During the manufacture of such devices, it is an essentially universal practice to functionally test the RF signal generating circuitry prior to shipment of the device to a customer.
The typical testing procedure for doing this comprises placing a small receiving antenna near an antenna on the wireless communication device. Test signals are transmitted between these antennas to test sensitivity, output power, and other parameters of the RF signal generating and receiving circuitry contained inside the device. In a cellular telephone, for example, two antennas may be provided, each of which can be used to transmit and receive RF signals. These two antennas may comprise a retractable monopole antenna for normal RF transmission by the customer when placing telephone calls, and a small helical antenna which remains external to the telephone body even when the antenna is retracted. The helical antenna can be used to receive RF signals initiated by a party placing a call to the cellular telephone. An example of such a system is disclosed in U.S. Pat. No. 5,353,036 to Baldry. With this configuration, the helical antenna may be used for transmitting and receiving signals to and from the test receiving antenna. Although acceptably precise measurements of the cellular telephone performance characteristics can be made with this system under some conditions, it is difficult to prevent the accumulation of small errors in the manufacturing environment which degrade the quality of the results obtained. Furthermore, in the manufacturing environment, where many phones may be tested simultaneously, interference from neighboring RF sources can affect measurement accuracy.
In spite of the drawbacks of this test methodology, wireless communication devices have generally not included suitable interface hardware for testing which does not rely on radiative coupling. In U.S. Pat. No. 5,394,162 to Korovesis, et al., these problems are considered in conjunction with the testing of cellular telephones mounted inside vehicles. In this case, the antenna is usually provided on an exterior surface of the vehicle, such as the rear window, to transmit the RF signals out of the vehicle itself. In particular, Korovesis et al. describe an RF coupler with a ground plane having a hole in its center which is placed over the antenna interface on the rear window prior to installation of the antenna. A semicircular contact is placed in electrical contact with the antenna interface base. Although this apparatus allows telephone testing without using the antenna element, interference can still be a problem. To help minimize such interference, a mesh EMI shield is preferably placed over the test apparatus during use.